1. Field of the Invention
The present invention relates to a process cartridge and a developer replenishment cartridge that are attachable/detachable to/from an electrophotographic image forming apparatus main body, and to an electrophotographic image forming apparatus employing these cartridges.
An electrophotographic image forming apparatus (hereinafter referred to as an “image forming apparatus”) is an apparatus configured to form an image on a recording medium by using an electrophotographic image forming process. Examples of an electrophotographic image forming apparatus include an electrophotographic copying machine, an electrophotographic printer (such as a light-emitting diode (LED) printer and a laser beam printer), an electrophotographic facsimile apparatus, and an electrophotographic word processor.
A recording medium is an object on which an image is formed, for example, a recording sheet and an overhead projector (OHP) sheet.
2. Description of the Related Art
Conventionally, an image forming apparatus has employed a process cartridge system in which an electrophotogrpahic photosensitive member and a process unit acting thereon are integrated into a cartridge, which is attachable/detachable to/from an image forming apparatus main body. The process cartridge system helps to achieve an improvement in terms of operability since it enables users to perform maintenance on the apparatus by themselves.
A process cartridge is formed by a cleaning unit and a development unit. The cleaning unit includes an image bearing member as an electrophotographic photosensitive member, and a cleaning member configured to clean the surface of the image bearing member. The development unit includes a development roller for supplying developer to the image bearing member, and a developer storage unit storing developer.
On the other hand, a developer replenishment system is known as an example of the process cartridge system. In this system, a developer replenishment opening of a developer replenishment cartridge and a developer reception opening of a process cartridge are detachably connected to each other, with developer being supplied from the developer replenishment cartridge to the process cartridge (See FIG. 4 on page 14 of Japanese Patent Application Laid-Open No. 2010-014890).
On the other hand, there has been proposed a system in which there are provided a light transmission type detection sensor for detecting the attachment condition of a process cartridge, and a sensor lever configured to act thereon, and the sensor lever is moved in conjunction with the attachment of the process cartridge to thereby detect the attachment condition of the process cartridge (See FIG. 2 on page 10 of Japanese Patent Application Laid-Open No. 2005-345939).